The unified power quality conditioner(UPQC) combines the function of series and shunt active filter which is the power equipment for manage various power quality problems. In common UPQC compensation control
the series converter only works during source voltage sag and does not participate in the load reactive power compensation. Therefore
the shunt converter often works in a state of heavy load. In addition
the common UPQC usually cannot work when there is a larger voltage drop or the source breaks off. We proposed a coordinated power control strategy of the UPQC with energy storage unit. By reasonably allocating the output power of the series and shunt converter
the function of the series converter is fully developed. In this scheme
the work voltage and current of the series converter are fixed at the rated value and thus it can share the burden of the shunt converter within the limitation of the capacity. Besides
the overcurrent risk of the feeder is eliminated since the source current is limited to the active component of load current under normal operating conditions with the utilization of energy storage unit. When the source voltage drops to zero
the load active power is supplied by the energy storage unit and the UPS(uninterruptible power supply) function is realized. The simulation is conducted in PSCAD/EMTDC
which shows that the proposed control strategy effectively reduces the vating configuration of UPQC by allocating the series/shunt converter and the energy storage unit of UPQC.